Polygon Inscribed Circle node

docs/nodes/analyzer/poly_inscribed_circle.rst

@@ -0,0 +1,68 @@
+Polygon Inscribed Circle
+========================
+
+Dependencies
+------------
+
+This node requires SciPy library to work.
+
+Functionality
+-------------
+
+This node calculates the center and the radius of inscribed circle for each
+convex face of the input mesh. Obviously, it is not always possible to inscribe
+a circle into a polygon, if polygon is not a triangle. For non-tiangular
+polygons, this node calculates the biggest circle which can be inscribed into
+the polygon, i.e. the circle which touches as many polygon edges as possible.
+
+Inputs
+------
+
+This node has the following inputs:
+
+- **Vertices**. The vertices of the input mesh. This input is mandatory.
+- **Faces**. The faces of the input mesh. This input is mandatory.
+
+Parameters
+----------
+
+This node has the following parameters:
+
+- **Flat Matrix output**. If checked, the node will generate a single flat list
+  of matrices in the **Matrix** output, for all input meshes. Checked by default.
+- **On concave faces**. This parameter is available in the N panel only.
+  Defines what the node should do if it encounters a concave face. There are
+  the following options available:
+
+  - **Skip**. Just skip such faces - do not generate inscribed circles for them.
+  - **Error**. Stop processing and give an error (turn the node red).
+  - **As Is**. Try to generate an inscribed circle for such face anyway. In
+    many cases, the generated circle will be incorrect (will be too small or
+    even outside the polygon), but in some simple cases it can be valid.
+
+  The default option is **Skip**.
+
+Outputs
+-------
+
+This node has the following outputs:
+
+- **Center**. For each inscribed circle, this contains a matrix, Z axis of
+  which points along face normal, and the translation component equals to the
+  center of the inscribed circle. This output can be used to actually place
+  circles at their places.
+- **Radius**. Radiuses of the inscribed circles.
+
+Examples of Usage
+-----------------
+
+In many cases inscribed circle can touch only two or three polygon edges:
+
+.. image:: ../../../docs/assets/nodes/analyzer/inscribed_circle_1.png
+   :target: ../../../docs/assets/nodes/analyzer/inscribed_circle_1.png
+
+If the polygon is almost regular, the circle will touch more edges:
+
+.. image:: ../../../docs/assets/nodes/analyzer/inscribed_circle_2.png
+   :target: ../../../docs/assets/nodes/analyzer/inscribed_circle_2.png
+

index.yaml

@@ -392,6 +392,7 @@
     - SvCircleApproxNode
     - SvSphereApproxNode
     - SvInscribedCircleNode
+    - SvSemiInscribedCircleNode
     - SvSteinerEllipseNode
     - ---
     - SvMeshSelectNodeMk2

menus/full_by_data_type.yaml

@@ -219,6 +219,7 @@
         - SvCircleApproxNode
         - SvSphereApproxNode
         - SvInscribedCircleNode
+        - SvSemiInscribedCircleNode
         - SvSteinerEllipseNode
         - ---
         - SvMeshSelectNodeMk2

menus/full_nortikin.yaml

@@ -446,6 +446,7 @@
         - SvCircleApproxNode
         - SvSphereApproxNode
         - SvInscribedCircleNode
+        - SvSemiInscribedCircleNode
         - SvSteinerEllipseNode
         - ---
         - SvMeshSelectNodeMk2

nodes/analyzer/poly_inscribed_circle.py

@@ -0,0 +1,96 @@
+# This file is part of project Sverchok. It's copyrighted by the contributors
+# recorded in the version control history of the file, available from
+# its original location https://github.com/nortikin/sverchok/commit/master
+#  
+# SPDX-License-Identifier: GPL3
+# License-Filename: LICENSE
+
+import numpy as np
+import bpy
+from bpy.props import BoolProperty, EnumProperty
+from sverchok.node_tree import SverchCustomTreeNode
+from sverchok.utils.inscribed_circle import calc_inscribed_circle, ERROR, RETURN_NONE, ASIS
+from sverchok.data_structure import updateNode, zip_long_repeat, ensure_nesting_level, get_data_nesting_level
+
+class SvSemiInscribedCircleNode(SverchCustomTreeNode, bpy.types.Node):
+    """
+    Triggers: Polygon Inscribed Circle
+    Tooltip: Inscribed circle for an arbitrary convex polygon
+    """
+    bl_idname = 'SvSemiInscribedCircleNode'
+    bl_label = 'Polygon Inscribed Circle'
+    bl_icon = 'OUTLINER_OB_EMPTY'
+    sv_icon = 'SV_POLY_INSCRIBED_CIRCLE'
+    sv_dependencies = {'scipy'}
+
+    def sv_init(self, context):
+        self.inputs.new('SvVerticesSocket', "Vertices")
+        self.inputs.new('SvStringsSocket', "Faces")
+        self.outputs.new('SvMatrixSocket', "Center")
+        self.outputs.new('SvStringsSocket', "Radius")
+
+    flat_output : BoolProperty(
+            name = "Flat Matrix output",
+            description = "Output single flat list of matrices",
+            default = True,
+            update = updateNode)
+
+    concave_modes = [
+            (RETURN_NONE, "Skip", "Skip concave faces - do not generate output for them", 0),
+            (ERROR, "Error", "Generate an error if encounter a concave face", 1),
+            (ASIS, "As Is", "Try to calculate inscribed circle anyway (it probably will be incorrect)", 2)
+        ]
+
+    on_concave : EnumProperty(
+            name = "On concave face",
+            description = "What to do if encounter a concave face",
+            default = RETURN_NONE,
+            items = concave_modes,
+            update = updateNode)
+
+    def draw_buttons(self, context, layout):
+        layout.prop(self, 'flat_output')
+
+    def draw_buttons_ext(self, context, layout):
+        self.draw_buttons(context, layout)
+        layout.label(text = "On concave faces:")
+        layout.prop(self, 'on_concave', text='')
+
+    def process(self):
+        if not any(socket.is_linked for socket in self.outputs):
+            return
+
+        vertices_s = self.inputs['Vertices'].sv_get()
+        vertices_s = ensure_nesting_level(vertices_s, 4)
+        faces_s = self.inputs['Faces'].sv_get()
+        faces_s = ensure_nesting_level(faces_s, 4)
+
+        matrix_out = []
+        radius_out = []
+        for params in zip_long_repeat(vertices_s, faces_s):
+            new_matrix = []
+            new_radius = []
+            for vertices, faces in zip_long_repeat(*params):
+                vertices = np.array(vertices)
+                for face in faces:
+                    face = np.array(face)
+                    circle = calc_inscribed_circle(vertices[face],
+                                    on_concave = self.on_concave)
+                    if circle is not None:
+                        new_matrix.append(circle.get_matrix())
+                        new_radius.append(circle.radius)
+                if self.flat_output:
+                    matrix_out.extend(new_matrix)
+                else:
+                    matrix_out.append(new_matrix)
+                radius_out.append(new_radius)
+
+        self.outputs['Center'].sv_set(matrix_out)
+        self.outputs['Radius'].sv_set(radius_out)
+
+def register():
+    bpy.utils.register_class(SvSemiInscribedCircleNode)
+
+def unregister():
+    bpy.utils.unregister_class(SvSemiInscribedCircleNode)
+

utils/geom.py

@@ -2801,3 +2801,24 @@ def scale_relative(points, center, scale):
 
     return (points + center).tolist()
 
+def is_convex_2d(verts):
+    """
+    Check if 2D polygon is convex.
+
+    Args:
+        verts: np.array or list of shape (n,3); only first and second components are considered.
+
+    Returns:
+        boolean.
+    """
+    verts = np.array(verts)
+    edges = np.roll(verts, -1, axis=0) - verts
+    sign = None
+    for e1, e2 in zip(edges[:-1], edges[1:]):
+        n = np.cross(e1, e2)
+        if sign is None:
+            sign = n[2]
+        elif sign * n[2] < 0:
+            return False
+    return True
+